The present invention relates to an image processing apparatus, more specifically to an image processing apparatus suitable for image processing in a color copying machine of a digital type, and especially to an image processing apparatus wherein even when a marker document on which an image processing region can be designated by a color marker, an ordinary color document and a black and white document are mixedly processed through the input therefrom, output of each document can be subjected to processing which is optimum for that document.
Up to now, there has been known a color copying machine of the so-called digital type wherein a document is scanned optically to form an optical image which is received by a line image sensor, for example, to be converted into electric signals. The electric signals are further digitized, and an electrostatic latent image is formed on a photoreceptor by a writing device such as a semiconductor laser based on the document image information converted to the aforementioned digital signals.
In a color copying machine, a color is reproduced by superposing a plurality of toner images, each having a color different from others (e.g., yellow Y, magenta M, cyan C and black Bk). In the case of a black and white document, a step of forming a toner image can be completed by forming only a black toner image, thereby it is possible to enhance productivity for copies, compared to that of a colored document.
Therefore, in some color copying machines of a digital type mentioned above, a document is discriminated in advance based on image information converted to the aforementioned digital signals whether the document is a color document or a black and white one. Based on the results of discrimination of the document, a copying process is performed through the mode which is suitable for the discriminated document.
In a copying machine equipped with a function to discriminate a document whether it is a color document or a black and white document as mentioned above, a type of each document to be copied can be discriminated and a processing mode suitable for the document type is selected automatically. Therefore, even when both a color document and a black and white document are set mixedly in an automatic document feeder (hereinafter, referred to as ADF), continuous copying has been possible through the mode suitable for each document.
Further, some color copying machines of the digital type mentioned above are equipped with a function of a partial color conversion process. The partial color conversion process, in this case, means an image editing process wherein image information inside (or outside) the region designated on a black and white document by a color marker can be converted to a color used for designating the region, for example, to be recorded.
When carrying out the partial color conversion process mentioned above, a user has been required to set on a copying machine a document (hereinafter referred to as a marker document) on which a region to be subjected to partial color conversion processing is designated with a color marker, and to select manually the mode for executing the aforementioned partial color conversion processing by operating a switch, for copying process.
Therefore, when marker documents are set on an ADF together with ordinary documents (a color document or a black and white document that is not designated by a color marker) other than a marker document, it has been impossible for these ordinary documents to be processed continuously under their own mode, with the marker documents processed in the same manner as in the ordinary document. However, it has been possible to set only a bundle of marker documents on an ADF for continuous operation of the mode for partial color conversion processing.